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Microsoft earns kudos in Linux conf keynote

"There is no direct evidence that that the entire stack has been subverted - we don't know if there's a generic attack that the NSA can use," he said.

Garrett told the audience that in his area of expertise, Microsoft was one of the few organisations providing the right balance between security and user freedoms.

Garrett, who currently works for cloud hardware company Nebula, told his fellow open source advocates that a key protection measure built into the Unified Extensible Firmware Interface (UEFI) - which provides the first step in starting up computers - was deployed correctly by Microsoft, but not by Google and Apple, both of which are avowed Open Source users.